Method of producing selenium coated electrodes



Sept. 2, 1941. c. KREu'z'ER 2,254,429l

METHOD OF PRDUCING SELENIM COATED ELECTRODES Filed Deo. 16, 1938 .l A c PMI Patented Sept. 2, 1941 METHOD F PRODUCING SELENIUM COATED ELEC'IRODES Conradin Kreutzer, Nuremberg; Germany Application y In December- 16, 193s, serial No. 246,231 Germany December 17, V1937 l 6 Claims. H.(Cl. F75-,466)

This inventionrelates to a method of producing selenium `rectiilers and selenium photo` cells.

In the production of selenium rectiflers and 'jselenium photo-cells, in which selenium acts as semi-conductor, considerable diiiicultiesare encountered in. obtaining the selenium in metallic modification from the metalloid in such a way as to produce a smooth surface or a surface of the desired form. If precautionary measures are not adopted during the process of conversion, the selenium tends to warp, and a rough honeycombed surface is produced, which is unv suitable for rectiers or photo-cells. Investigations have shown that the reason for this conas possible, and in particular vthe imprisonment of air should be avoided. Owing to the. surface contact a large number of crystallisation centres are produced, which are'distributed evenly over the layer of selenium, and from which the crystais develop in correspondingly even distribution towards the interiorA of the layer.

In this way there is obtained an evenly/ metallically crystallized selenium layer having a smooth surface, the form of which depends on the form of the base plate and on the form of the contacting surface.

In carrying out the invention the selenium is not fused onto the supporting electrode, but onto a material, such as aluminum, which does not enter into connection, or into conductive connection,with the selenium. The selenium can be applied to the material, which is preferably in the form 'of a foil, by a spraying operation, or it can be deposited thereon accordingto any of the conventional processes. A particularly convenient method has been found to consist in applying the amorphous selenium to the foil at a temperature which-is below the fusing point of the crystallineselenium. The foil 'is then applied to the supporting electrode with the seleniuml downwards, preferably under a lslight trode merely requires to have a temperature below the fusing point of the crystalline selenium,

lor below 220 C. The foil, the amorphous selenium and the supporting plate are now connected 45 together. 'Ihe foil can be. readily stripped off.

'I'his can' be performed either after the forming or after the selenium has been allowed to cool.`

The invention is illustrated by way of example in the accompanying drawing, in which Fig. 1 is a sectional view of a metal foil showing the selenium applied thereto.

Fig. 2 is a. sectional view illustrating the methiod of applying the selenium to an electrode.

In Figs. 1 and 2 therev are shown the metal ling surface 3a, which in this case consists, for example, of a thin foil of.. aluminum. The selenium 2a isl applied to the foil 3a, for. example in a spraying operation, whereupon the foil with the layer 2a directed downwards is .applied to the electrode la, which has either been heated or is then1heated in the manner referred to. After the application the foil 3a is caused v'to 5 bear intimately against the plate la, for exam- 2 the cooling the foil 3aV can be readily stripped oil?.

Themethod described oii'ers considerable ad! vantages as compared with known procel which the selenium is fusedl onto the supporting electrode and inv which it isnecessary to raise the electrode to a temperature which is atleast Y a few degrees above the fusingfpoint of the selenium. In the latter case the selenium combines with the electrode to form selenide and the properties of the rectiiler or the photo-cell are thus impaired. Y

What I claim as newland desire to secure by Letters Patent is:

1. The method of producing selenium coated 40' electrodes which consists in applying a layer o f amorphous selenium to a metal foil, arranging the layer of selenium carried by the foil in intimate contact with an electrode, subjecting the electrodeA andthe foil to'pressure to expel air from the selenium, maintaining the electrode and the foilat a temperature for converting the selenium into a crystalline state, cooling the selenium, and removing the foil.

2. The method of producing selenium coated '50 electrodes which consists in, spraying selenium onto an aluminum foil to provide a relatively .thin layer of selenium thereon, arranging the layer of selenium carried by the foil over an electrode, rolling the foil to press'the 'selenium f pressure to expel any air. The supporting elecinto intimate contact with the electrode, heating electrode la, the selenium 2a, and the contactple by passing a roller l over the-same. After steamv the selenium to convert thesame into a crystalline state. cooling the selenium,A and removing the foil.

3. The method of vproducing selenium coated electrodes which consists in, coating a metal foil with selenium to provide a' layer thereon. arranging the selenium carried by the foil over an electrode, rolling the foil to provide intimate conremoving the foil.

4. The method oi' producing selenium coated #metallic electrodes which consists in,V applying a tact of the selenium with the electrode, and

' 15 foil.

5. The method of producing selenium coated electrodes which lconsists in. applying selenium in an amorphous condition to a foil, arranging the selenium carried by the foil in contact with an electrode, heating the selenium to a temperature not exceeding 220 C., cooling the selenium, and removing the foil. f

6. The method of producing selenium coated electrodes which consists in, spraying selenium in a finely divided condition onto a foil, heating an electrode to a temperature sumcient for rendering the selenium crystalline, applying the selenium carried by the foil onto the heated electrode, cooling the electrode, and removing the coNRAmN KREUTZER. 

